From: Martin DeMello <martindemello@...>
Date: 2003-08-30T00:38:44+09:00
Subject: Re: multiply all array with array

ibotty <me@ibotty.net> wrote:
> thx all ya guys,
> 
>>> is there a builtin function in array.rb (that i have missed).
>> 
>> Not quite, but for parallel traversing made easier
>> 
>> a.zip(b).map {|i, j| i*j}
> 
> this is indeed much more elegant.
> 
> but because array * array is not defined, me thinks. one could implement
> (this simple case) this way.

Here's a handy generalisation of the method:

class Array
  def mapwith(*args, &block)
    if block_given?
      zip(*args).collect {|i, j| yield i, j}
    else
      f = args.pop
      zip(*args).collect {|i, j| i.send(f, j)}
    end
  end
end

p [1,2,3].mapwith([4,5,6]) {|i,j| i*j}
p [1,2,3].mapwith([4,5,6], :*) 

martin